Energy saving is the most important policy for industries in the whole world. With the development of the IT industry, the energy consumed by the application of IT equipment occupies higher and higher proportion in energy consumption. In order to guarantee the reliable and uninterruptible operation of information equipment (such as IDCs (Internet Data Center), banks, insurance, stock markets, wireless communication base stations, repeaters, various EPON devices, security equipment and fire monitoring systems), a plurality of UPSes (Uninterruptible Power Source) are connected between sensitive equipment and a power supply network in series. In a series system formed by the power supply network, the UPSes and the sensitive equipment (load), the UPSes must be subjected to main energy conversion twice completely in order to avoid the 1% power-off possibility of the sensitive equipment.
If the reliability of the electric network is L %, the reliability of the UPSes being U %, and the total power supply reliability of the system being P %,
P %=U %, which means that the safe power supply of the system can only be guaranteed when the UPSes are normal.
Therefore, if the “function utilization” of the UPSes is F %,F%=(1−L%)−(1−U%)=U%−L%.
The formula of the “total resources utilization” is as follows:Total Resources Utilization=Function Utilization×(Purchasing Cost×Annual Depreciation Rate+Annual Energy Consumption Cost+Maintenance Cost)
It can be easily seen that the “resources utilization” of the UPSes is the minimum among all the power conversion devices.
Moreover, an AC passes through the UPSes and SMPSes (Switch Mode Power Supply) of the equipment and arrives at ultimate loads of the equipment. Due to the efficiency of the UPSes of less than 100% and the no-load standby power consumption, energy of 3% or higher may be consumed.
As the traditional UPS power supply protection mode has the inherent defects, a 240 Vdc power supply proposal, a 48 Vdc power supply proposal and certain AC/DC−DC/DC proposals have been adopted in the telecommunication industry, IDC machine rooms and the like currently. However, in all the methods, one energy conversion unit must be connected in series on the front of the sensitive equipment, and then the methods also have the defects of energy consumption and resource waste.
The Chinese invention patent No. ZL021344558 discloses a self-coupling mutual inductance uninterruptible switching power supply, wherein the core technology thereof is to introduce a second energy low-voltage DC and find out an optimal entry point according to the turn ratio of primary and secondary windings. However, there is 1% to 3% energy loss in low-voltage DC circuits during the high-voltage operation.